The fossil record of terrestrial mammals in Antarctica is temporally and geographically constrained to the Eocene outcrops of La Meseta and Submeseta formations in Seymour (Marambio) Island in West Antarctica. The faunal assemblage indicates a clear South American imprint since all the groups have a close phylogenetic relationship with Cretaceous and Paleogene mammals from Patagonia. Despite the presence of several mammalian taxonomic groups: Dryolestida, Gondwanatheria, Eutheria and Metatheria; the presence of other major mammalian taxa should be expected and will probably be confirmed by new findings. Placental mammals with an inferred body mass between 10 to 400 kg size, are represented by xenarthrans, and two groups of the so called South American native ungulates: Astrapotheria and Litopterna. The Metatheria are the smaller (less than 1 kg) and most abundant components of the fauna. Marsupials are represented by derorhynchid ameridelphians; several microbiotherian australidelphians, a ?microbiotheriid and a woodburnodontid; and prepidolopid and polydolopid polydolopimorphians. Plus, there are remains of several mammalian teeth of indeterminate phylogenetic affinities. The present knowledge of the Southern Hemisphere mammalian evolution and paleogeographic change through time, indicates that Antarctica played a major role for land mammals, at least since the Jurassic. The actual representation of Paleogene terrestrial mammals in Antarctica is clearly biased, as all the evidence indicates that australosphenidan mammals should be present in Antarctica since the Jurassic.